1. Field of the Invention
This invention relates to handling small articles, such as, for example, electronic component chips. More particularly, the invention relates to a tape for temporarily holding the chips. Mounted to the tape, the chips are dispensed to a processing location, such as a bonder. At the bonder the tape is indexed past a bond station where the chips are bonded, in sequence, to sites on a substrate. The particular embodiment of the invention is described with respect to a compliant bonding tape which is adapted to temporarily retain beam-lead semiconductor chips. But, as can be seen from the detailed description, the invention lends itself in a broader sense to handling other small articles as well.
2. Description of the Prior Art
In the semiconductor industry, small semiconductor chips are often bonded to substrates, and conductive elements are interconnected to leads extending from the substrates. U.S. Pat. No. 3,533,155 to A. Coucoulas describes a process of compliantly bonding beam-lead chips to substrates. In U.S. Pat. No. 3,640,444 to D. P. Ludwig, a compliant tape is disclosed which is interposed between the chip and a bonding tool or thermode during bonding. U.S. Pat. No. 3,858,721 to Boyer et al. discloses a further advance in the art wherein the compliant tape is used as a means for temporarily holding the chips to be bonded on the tape. The disclosed tape has periodic depressions of a size which permit beam leads of the chips to rest in such depressions while the body of each of the chips becomes located in a central aperture through each of the depressions. In the process of transferring the chips from the tape to bond sites on respective substrates, the thermode bears against the side of the tape opposite each depression to force the beam leads against the substrate, whereby the chip becomes bonded to the substrate. The material of the tape in the area of the depressions serves as the compliant member between the thermode and the beam leads.
Another advance of the prior art is depicted in FIG. 2 hereof. There, a dual embossment raises each depression from the plane of the tape so that only a small area about the depression actually comes into contact with the substrate to which the chip is to be bonded.
An area of concern in using tapes as temporary packages for beam-lead chips in accordance with the prior art has been the forming of the described embossments and depressions or nesting embossments for the chips in the tape. To ultimately form bonds with a uniform compressive force it is desirable to actually shear the compliant material about the periphery of the nesting embossment with a uniformly repetitive shear force requirement. The depth to which the embossment has to be pushed to establish such a complete shear varies with the material. Therefore, a particular die for embossing the tape is designed for a particular alloy and temper of compliant material.
It has also been observed that when the chips are handled in and then bonded in a transfer from the prior art tape packages, sheared embossments tend to separate from the tape and remain on the substrates with the bonded chips. While such remaining embossments are easily detected and removed, removing them nevertheless involves an additional operation which is desirably eliminated.